Zoom lens, and video camera and digital still camera using the zoom lens

ABSTRACT

A zoom lens, having a camera shake correction function, that is capable of preventing degradation of chromatic aberration while correcting camera shake, and can be small, light-weight and power-saving, is provided. The zoom lens is composed of four groups of lenses having positive, negative, positive and positive refractive powers, arranged in that order from an object side to an image plane side, where a second lens group conducts zooming and a fourth lens group conducts focus adjustment. The second lens group is made of a concave meniscus lens, a concave lens, a double convex lens, and a concave lens, arranged in that order from the object side to the image plane side, and it includes also at least one aspheric surface. A third lens group includes a cemented lens having a cemented surface whose convex surface faces the object side, and can be shifted in a perpendicular direction with respect to an optical axis in order to correct image fluctuations during a camera shake.

TECHNICAL FIELD

The present invention relates to a zoom lens that is used for a videocamera or the like, and that is provided with a function for opticallycorrecting image shake caused by camera shake or vibrations; and a videocamera and a digital still camera using such a zoom lens.

BACKGROUND ART

In recent years, in imaging systems such as video cameras, an anti-shakefunction that prevents vibrations such as camera shake has becomeindispensable, and various types of anti-shake optical systems have beenproposed.

For example, in the video camera disclosed in JP H8-29737A, an opticalsystem for correcting camera shake made of two lenses is placed in frontof a zoom lens, and image fluctuations due to camera shake are correctedby shifting one of those lenses perpendicularly with respect to theoptical axis.

In the video camera disclosed in JP H7-128619A, a zoom lens made of fourlens groups is used, and image fluctuations due to camera shake arecorrected by shifting a part of the third lens group made of a pluralityof lenses perpendicularly with respect to the optical axis.

However, in the video camera disclosed in JP H8-29737A, since theoptical system for correcting camera shake is placed in front of thezoom lens, the lens diameter of the optical system for correcting camerashake becomes large. As a consequence, the video camera itself alsobecomes larger, and the load on the driving system becomes larger, whichis disadvantageous with regard to making the video camera smaller andlighter, and reducing its power consumption.

Furthermore, in the video camera disclosed in JP H7-128619A, imagefluctuations due to camera shake are corrected by shiftingperpendicularly with respect to the optical axis some of the lenses ofthe third lens group that is fixed with respect to the image plane, sothat it is advantageous with regard to size compared to video cameras inwhich the optical system for correcting camera shake is placed in frontof the zoom lens, but since a part of the third lens group is moved,degradation of chromatic aberration during correction of camera shakecannot be avoided.

DISCLOSURE OF INVENTION

It is an object of the present invention to solve the above-describedproblems of the related art, and to present a zoom lens composed of fourlens groups, in which camera shake can be corrected by shifting a thirdlens group that is fixed as a whole with respect to the image plane, ina perpendicular direction with respect to the optical axis when zoomingand focusing. The zoom lens also can prevent degradation of chromaticaberration during correction of camera shake. The present inventionpresents a video camera and a digital still camera using this zoom lens,which can be smaller in size, lighter in weight and power-saving.

In order to attain this object, a first configuration of a zoom lens inaccordance with the present invention includes:

a first lens group that includes a lens having negative refractive powerand a lens having positive refractive power, as well as a lens havingpositive refractive power, arranged in that order from an object side toan image plane side, the first lens group having an overall positiverefractive power and being fixed with respect to an image plane;

a second lens group having an overall negative refractive power, a zoomoperation being carried out by shifting the second lens group on anoptical axis;

an aperture stop that is fixed with respect to the image plane;

a third lens group that is made of a lens having positive refractivepower, as well as a lens having a positive refractive power, and a lenshaving negative refractive power, arranged in that order from the objectside to the image plane side, the third lens group having an overallpositive refractive power and being fixed with respect to the opticalaxis direction when zooming or focusing; and

a fourth lens group that is made of a lens having positive refractivepower, a lens having negative refractive power and a lens havingpositive refractive power, arranged in that order from the object sideto the image plane side, the fourth lens group having an overallpositive refractive power and being shifted on the optical axis so as tomaintain the image plane that fluctuates when the second lens group isshifted on the optical axis and when the object moves, at a certainposition from a reference plane;

wherein the second lens group is made of a concave meniscus lens, aconcave lens, a double convex lens and a concave lens, arranged in thatorder from the object side to the image plane side, and includes atleast one aspheric surface;

wherein the third lens group includes a cemented lens having a cementedsurface whose convex surface faces the image plane side, the third lensgroup can be shifted in a direction perpendicular to the optical axis inorder to correct image fluctuations during camera shake, and includes atleast one aspheric surface; and

wherein the fourth lens group includes at least one aspheric surface.

According to the first configuration of a zoom lens, a zoom lens havinga function of correcting camera shake, which is also capable ofpreventing degradation of chromatic aberration during camera shake andcan be smaller in size, lighter in weight and power-saving, can beprovided.

Also, in the first configuration of the zoom lens of the presentinvention, it is preferable that the fourth lens group is made of aconcave lens, a convex lens and a concave lens, arranged in that orderfrom the object side to the image plane side, and that all of theselenses are cemented together.

It is also preferable in the first configuration of the zoom lens of thepresent invention that the fourth lens group is made of three lenses andthat all of these lenses are cemented together, which satisfiesconditions of the following Expressions (1) and (2) when τ₃₇₀ indicatestransmittance of light having a wavelength of 370 nm and τ₃₈₀ indicatestransmittance of light having a wavelength of 380 nm at a part of a lenswhere the thickness is 10 nm, the lens being the second in the fourthlens group when viewed from the object side.0.02<τ₃₇₀<0.2  (1)0.2<τ₃₈₀<0.55  (2)

By configuring the fourth lens group with three lenses, aberrations suchas chromatic aberration can be corrected favorably. Also, sincecementing all of the three lenses together corresponds to combining onelens, the tolerance can be relieved.

Expressions (1) and (2) define transmittance in an ultraviolet ray (UV)wavelength region of a lens positioned in the midst of the cementedlenses. For cementing three lenses, as shown in FIG. 1, two lenses firstare cemented together, and then a third lens is cemented thereto. Whencementing the third lens, the previously cemented parts are alsoUV-irradiated. This may lead to excessive UV irradiation, therebydegrading strength at the first cemented surfaces and thus it may resultin peeling of the bonded surfaces. Therefore, regarding the material ofthe center lens, it is necessary to define the transmittance in the UVwavelength region. Above the upper limits of Expressions (1) and (2),the transmittance in the UV wavelength region is increased extremely,which will cause difficulty in favorably cementing the three lenses. Onthe contrary, below the lower limit of Expressions (1) and (2),sufficient UV irradiation for a permanent curing cannot be performed,and thus the previously cemented parts will have insufficient strengthand may be peeled easily.

A second configuration of a zoom lens in accordance with the presentinvention includes:

a first lens group that includes a lens having negative refractive powerand a lens having positive refractive power, as well as a lens havingpositive refractive power, arranged in that order from an object side toan image plane side, the first lens group having an overall positiverefractive power and being fixed with respect to an image plane;

a second lens group having an overall negative refractive power, a zoomoperation being carried out by shifting the second lens group on anoptical axis;

an aperture stop that is fixed with respect to the image plane;

a third lens group that is made of a lens having positive refractivepower, as well as a lens having positive refractive power and a lenshaving negative refractive power, arranged in that order from the objectside to the image plane side, the third lens group having an overallpositive refractive power and being fixed with respect to the opticalaxis direction when zooming or focusing; and

a fourth lens group that is made of a lens having positive refractivepower, a lens having negative refractive power and a lens havingpositive refractive power, arranged in that order from the object sideto the image plane side, the fourth lens group having an overallpositive refractive power and being shifted on the optical axis so as tomaintain the image plane that fluctuates when the second lens group isshifted on the optical axis and when the object moves, at a certainposition from a reference plane;

wherein the second lens group includes at least one aspheric surface;

wherein the third lens group is made of three single lenses including aconvex lens, a concave lens and a convex lens, arranged in that orderfrom the object side to the image plane side, and can be shifted in adirection perpendicular to the optical axis in order to correct imagefluctuations during camera shake, and includes at least one asphericsurface; and

wherein the fourth lens group is made of three single lenses andincludes at least one aspheric surface.

According to this second configuration of a zoom lens, particularly byconfiguring the third and fourth lens groups with single lenses alone,the design parameter is increased to allow improvement of theperformance.

A third configuration of a zoom lens in accordance with the presentinvention includes:

a first lens group that includes a lens having negative refractive powerand a lens having positive refractive power, as well as a lens havingpositive refractive power, arranged in that order from an object side toan image plane side, the first lens group having an overall positiverefractive power and being fixed with respect to an image plane;

a second lens group having an overall negative refractive power, a zoomoperation being carried out by shifting the second lens group on anoptical axis;

an aperture stop that is fixed with respect to the image plane;

a third lens group that is made of a lens having positive refractivepower, as well as a lens having a positive refractive power, and a lenshaving negative refractive power, arranged in that order from the objectside to the image plane side, the third lens group having an overallpositive refractive power and being fixed with respect to the opticalaxis direction when zooming or focusing; and

a fourth lens group being shifted on the optical axis so as to maintainthe image plane that fluctuates when the second lens group is shifted onthe optical axis and when the object moves, at a certain position from areference plane;

wherein the second lens group is made of a concave meniscus lens, adouble concave lens, a double convex lens and a convex lens, arranged inthat order from the object side to the image plane side, and includes atleast one aspheric surface;

wherein the third lens group is made of a double convex lens and also acemented lens including a convex lens and a concave lens, arranged inthat order from the object side to the image plane side, which can beshifted in a direction perpendicular to the optical axis in order tocorrect image fluctuations during camera shake and includes at least oneaspheric surface; and

wherein the fourth lens group is made of one convex lens and includes atleast one aspheric surface.

According to the third configuration of the zoom lens, by configuringthe fourth lens group with one convex lens, the manufacturing cost islowered and the assembly tolerance can be relieved.

In the first to third configurations of the zoom lens of the presentinvention, it is preferable that the conditions of the followingExpressions (3) and (4) are satisfied when RIH indicates image height,f₁ indicates a focal length of the first lens group, and f₂ indicates afocal length of the second lens group.2.0<|f ₂ /RIH|<3.0  (3)0.16<|f ₂ /f ₁|<0.22  (4)

Expression (3) is a condition for appropriately defining the focallength of the second lens group and for realizing both high performanceand size reduction. Since the required focal length varies depending onthe frame size, it is normalized by a frame size. Above the upper limitof Expression (3), the variation in the aberration during a shift of thesecond lens group when zooming is relieved, but the shifting distancebecomes large, thereby hindering the size reduction.

Expression (4) defines the focal length of the first lens group, whichis required after Expression (3) is satisfied. Above the upper limit ofExpression (4), the first lens group will have excessive power,resulting in flare. Particularly, flare of lower light beams will occureasily, from the standard position to the tele end. Below the lowerlimit of Expression (4), less flare will occur. However, since the powerof the first lens group is weakened excessively, longitudinal chromaticaberration will occur easily at the tele end.

In the first to third configurations of the zoom lens of the presentinvention, it is preferable that the condition of the followingExpression (5) is satisfied when f₁ indicates a focal length of thefirst lens group, and f₁₁₋₁₂ indicates a combined focal length of afirst lens and a second lens of the first lens group viewed from theobject side.3.2<f ₁₁₋₁₂ /f ₁<5.0  (5)

Expression (5) is a condition for favorably correcting longitudinalchromatic aberration and coma aberration at the tele end. Above theupper limit of Expression (5), the power of the cemented surfaces willbe weakened, and thus sufficient achromatism cannot be obtained. As aresult, the longitudinal chromatic aberration at the tele end will bemagnified. On the contrary, below the lower limit of Expression (5),since the power of the cemented surfaces will be excessively strong withrespect to the entire focal length, coma flare will occur easily fromthe standard position to the tele end.

In the first to third configurations of the zoom lens of the presentinvention, it is also preferable that the condition of the followingExpression (6) is satisfied when f₁₃ indicates a focal length of a thirdlens of the first lens group viewed from the object side, and f₁₃₂indicates a focal length of a surface of the third lens of the firstlens group, facing the image plane when viewed from the object side.−2.5<f ₁₃₂ /f ₁₃<−1.5  (6)

Expression (6) is a condition for favorably correcting distortion andcoma aberration. Above the upper limit of Expression (6), astigmatism isovercorrected, thereby enlarging a barrel distortion. Below the lowerlimit of Expression (6), coma flare will occur easily and enlarge apin-cushion distortion.

In the first to third configurations of the zoom lens of the presentinvention, it is also preferable that the condition of the followingExpression (7) is satisfied when dsag_(2i1) indicates an aspheric amountat the 10% effective aperture of an ^(i-th) aspheric surface of thesecond lens group viewed from the object side, and dsag_(2i9) indicatesan aspheric amount at the 90% effective aperture of an ^(i-th) asphericsurface of the second lens group viewed from the object side.−0.23<dsag _(2i1) /dsag _(2i9)<−0.10  (7)

Expression (7) is a condition for favorably correcting coma aberration.In a case where an aspheric surface is used for the concave surface,above the upper limit of Expression (7), the aspheric amount in thevicinity of the effective aperture is decreased excessively, thereforecoma flare of the lower light beams will not be corrected sufficiently,particularly at the periphery of the picture plane in a range from thewide-angle end to the standard position. On the contrary, below thelower limit of Expression (7), the coma flare is overcorrected. When anaspherical surface is used for a convex surface, the operation isperformed in a reversed manner.

In the first to third configurations of the zoom lens of the presentinvention, it is also preferable that the aspheric surface of the secondlens group is arranged the closest to the image plane side, and that theconcave surface faces the image plane side. Since an off-axis principallight beam height becomes low on the surface of the second lens grouparranged closest to the image plane, according to this preferredexample, the coma aberration can be corrected without having muchinfluence on the astigmatism. Moreover, since the concave surface facesthe image plane side, the pin-cushion distortion occurring at a positionbetween a wide-angle end and a standard position can be correctedfavorably.

In the first to third configurations of the zoom lens of the presentinvention, it is also preferable that the condition of the followingExpression (8) is satisfied when dsag_(3i1) indicates an aspheric amountat the 10% effective aperture of an ^(i-th) aspheric surface of thethird lens group viewed from the object side, and dsag_(3i9) indicatesan aspheric amount at the 90% effective aperture of an ^(i-th) asphericsurface of the third lens group viewed from the object side.−0.24<dsag _(3i1) /dsag _(3i9)<−0.15  (8)

Expression (8) is a condition for favorably correcting sphericalaberration. The third lens group, at which the light flux has a largediameter, has a particularly great influence on the longitudinalperformance. In a case where an aspheric surface is used for the convexsurface, above the upper limit of the Expression (8), light beams on theaxis are overcorrected. Below the lower limit of Expression (8), thelight beams on the axis are corrected insufficiently When an asphericalsurface is used for a concave surface, the operation is performed in areversed manner.

In the first to third configurations of the zoom lens of the presentinvention, it is also preferable that the condition of the followingExpression (9) is satisfied when dsag_(4i1) indicates an aspheric amountat the 10% effective aperture of an ^(i-th) aspheric surface of thefourth lens group viewed from the object side, and dsag_(4i9) indicatesan aspheric amount at the 90% effective aperture of an ^(i-th) asphericsurface of the fourth lens group viewed from the object side.−0.45<dsag _(4i1) /dsag _(4i9)<−0.13  (9)

Expression (9) is a condition for favorably correcting coma aberration.The fourth lens group has a great influence on performance of off-axislight beams, and particularly, performance of upper light beams. In acase where an aspheric surface is used for the convex surface, above theupper limit of Expression (9), the aspheric surface amount at theperiphery is decreased excessively, therefore the off-axis upper lightbeams at the periphery of the picture plane is overcorrected. On thecontrary, below the lower limit of Expression (9), the correction willbe insufficient. When an aspherical surface is used for a concavesurface, the operation is performed in a reversed manner.

In the first to third configurations of the zoom lens of the presentinvention, it is also preferable that the condition of the followingExpression (10) is satisfied when RIH indicates an image height, Sg_(i)indicates a specific gravity of each lens and CL_(i) indicates a lensdiameter of each lens in the third lens group. $\begin{matrix}{{\sum\limits_{i = 1}^{n}{\left( {{Sg}_{i} \cdot {CL}_{i}^{2}} \right)/{RIH}}} < 50} & (10)\end{matrix}$

The third lens group shifts as a whole in a direction perpendicular tothe optical axis in order to correct fluctuations of the image duringcamera shake. When correcting the camera shake, for operating the lensgroup constantly, the power consumption is increased with the increasein weight. Since thrust is also necessary, a large-sized actuator isrequired. Expression (10) is a condition for formulating the weight ofthe third lens group. The lens weight is proportional to squares of thespecific gravity and the lens diameter. The lens size varies dependingon the image height, and since the size allowance of an applicableactuator will vary the lens size is normalized by the image height.Above the upper limit of Expression (10), both the lens barrel and thepower consumption will be increased excessively.

A video camera according to the present invention is configured as avideo camera having a zoom lens, where the zoom lens of the presentinvention is used.

A digital still camera according to the present invention is configuredas a digital still camera having a zoom lens, where the zoom lens of thepresent invention is used.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A and FIG. 1B are schematic views showing a method of cementingthree lenses.

FIG. 2 is a block diagram showing a basic configuration of a zoom lenshaving a camera shake correction function according to the presentinvention.

FIG. 3 is a layout illustrating the configuration of a zoom lensaccording to Example 1 of the present invention.

FIGS. 4A-4E show aberration graphs for the wide-angle end of the zoomlens in Example 1 of the present invention.

FIGS. 5A-5E show aberration graphs for the standard position of the zoomlens in Example 1 of the present invention.

FIGS. 6A-6E show aberration graphs for the tele end of the zoom lens inExample 1 of the present invention.

FIGS. 7A-7C show the aberration graphs during a camera shake correctionat the tele end in Example 1 of the present invention.

FIGS. 8A-8E show aberration graphs for the wide-angle end of the zoomlens in Example 2 of the present invention.

FIGS. 9A-9E show aberration graphs for the standard position of the zoomlens in Example 2 of the present invention.

FIGS. 10A-10E show aberration graphs for the tele end of the zoom lensin Example 2 of the present invention.

FIGS. 11A-11C show the aberration graphs during a camera shakecorrection at the tele end in Example 2 of the present invention.

FIG. 12 is a layout illustrating the configuration of a zoom lensaccording to Example 3 of the present invention.

FIGS. 13A-13E show aberration graphs for the wide-angle end of the zoomlens in Example 3 of the present invention.

FIGS. 14A-14E show aberration graphs for the standard position of thezoom lens in Example 3 of the present invention.

FIGS. 15A-15E show aberration graphs for the tele end of the zoom lensin Example 3 of the present invention.

FIGS. 16A-16C show the aberration graphs during a camera shakecorrection at the tele end in Example 3 of the present invention.

FIG. 17 is a layout illustrating the configuration of a zoom lensaccording to Example 4 of the present invention.

FIGS. 18A-18E show aberration graphs for the wide-angle end of the zoomlens in Example 4 of the present invention.

FIGS. 19A-19E show aberration graphs for the standard position of thezoom lens in Example 4 of the present invention.

FIGS. 20A-20E show aberration graphs for the tele end of the zoom lensin Example 4 of the present invention.

FIGS. 21A-21C show the aberration graphs during a camera shakecorrection at the tele end in Example 4 of the present invention.

FIG. 22 is a layout illustrating a configuration of a video cameraaccording to a fourth embodiment of the present invention.

FIG. 23 is a perspective view showing a configuration of a digital stillcamera according to a fifth embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be explained below more specifically, byreferring to some embodiments.

FIG. 2 shows a basic configuration of a zoom lens provided with a camerashake correction function according to the present invention. As shownin FIG. 2, a zoom lens of the present invention consists of four lensgroups composed of a first lens group, a second lens group, a third lensgroup and a fourth lens group, arranged in that order from an objectside to an image plane side. In this case, the second lens groupconducts zooming, and the fourth lens group conducts focus adjustment.Moreover, by shifting the third group in a perpendicular direction withrespect to the optical axis, image fluctuations during camera shake arecorrected.

First Embodiment

A zoom lens in this embodiment includes:

a first lens group that includes a lens having negative refractive powerand a lens having positive refractive power, as well as a lens havingpositive refractive power, arranged in that order from an object side toan image plane side, the first lens group having an overall positiverefractive power and being fixed with respect to an image plane;

a second lens group that is made of a concave meniscus lens, a concavelens, a double convex lens and a concave lens, arranged in that orderfrom an object side to an image plane side, the second lens group havingan overall negative refractive power, a zoom operation being carried outby shifting the second lens group on an optical axis;

an aperture stop that is fixed with respect to the image plane;

a third lens group that is made of a lens having positive refractivepower, as well as a lens having a positive refractive power and a lenshaving negative refractive power, arranged in that order from the objectside to the image plane side, the third lens group having an overallpositive refractive power and being fixed with respect to the opticalaxis direction when zooming or focusing; and

a fourth lens group that is made of a lens having positive refractivepower, a lens having negative refractive power and a lens havingpositive refractive power, arranged in that order from the object sideto the image plane side, the fourth lens group having an overallpositive refractive power and being shifted on the optical axis so as tomaintain the image plane that fluctuates when the second lens group isshifted on the optical axis and when the object moves, at a certainposition from a reference plane.

The third lens group includes a cemented lens having a cemented surfacewhose convex surface faces the image plane side, and can be shifted in adirection perpendicular to the optical axis in order to correct imagefluctuations during camera shake.

Furthermore, the second lens group, the third lens group or the fourthlens group includes at least one aspheric surface.

It should be noted that such an aspherical surface is defined by thefollowing Equation 1 (this also applies to the following Second andThird Embodiments). $\begin{matrix}{{SAG} = {\frac{H^{2}/R}{1 + \sqrt{1 - {\left( {1 + K} \right)\left( {H/R} \right)^{2}}}} + {D \cdot H^{4}} + {E \cdot H^{6}} + {F \cdot H^{8}} + {G \cdot H^{10}}}} & \left( {{Equation}\quad 1} \right)\end{matrix}$

In Equation 1, H denotes the height from the optical axis, SAG denotesthe distance from the vertex on the aspherical surface at a height Hfrom the optical axis, R denotes the radius of curvature at the vertexof the aspherical surface, K denotes a conic constant, and D, E, F, Gdenote aspheric coefficients.

It is preferable that the fourth lens group is made of a concave lens, aconvex lens and a concave lens, arranged in that order from the objectside to the image plane side, and that all of these lenses are cementedtogether.

In the zoom lens of this embodiment, all of the lenses in the fourthlens group are cemented together, and preferably, conditions of thefollowing Expressions (1) and (2) are satisfied when τ₃₇₀ indicatestransmittance of light having a wavelength of 370 nm and τ₃₈₀ indicatestransmittance of light having a wavelength of 380 nm at a part of a lenswhere the thickness is 10 nm, the lens is the second in the fourth lensgroup when viewed from the object side.0.02<τ₃₇₀<0.2  (1)0.2<τ₃₈₀<0.55  (2)

In the zoom lens of this embodiment, it is preferable that theconditions of the following Expressions (3) and (4) are satisfied whenRIH indicates image height, f₁ indicates a focal length of the firstlens group, and f₂ indicates a focal length of the second lens group.2.0<|f ₂ /RIH|<3.0  (3)0.16<|f ₂ /f ₁|<0.22  (4)

In the zoom lens of this embodiment, it is preferable that the conditionof the following Expression (5) is satisfied when f₁ indicates a focallength of the first lens group, and f₁₁₋₁₂ indicates a combined focallength of a first lens and a second lens of the first lens group viewedfrom the object side.3.2<f ₁₁₋₁₂ /f ₁<5.0  (5)

In the zoom lens of this embodiment, it is also preferable that thecondition of the following Expression (6) is satisfied when f₁₃indicates a focal length of a third lens of the first lens group viewedfrom the object side, and f₁₃₂ indicates a focal length of a surface ofthe third lens of the first lens group facing the image plane whenviewed from the object side.−2.5<f ₁₃₂ /f ₁₃<−1.5  (6)

In the zoom lens of this embodiment, it is also preferable that thecondition of the following Expression (7) is satisfied when dsag_(2i1)indicates an aspheric amount at the 10% effective aperture of an ^(i-th)aspheric surface of the second lens group viewed from the object side,and dsag_(2i9) indicates an aspheric amount at the 90% effectiveaperture of an ^(i-th) aspheric surface of the second lens group viewedfrom the object side.−0.23<dsag _(2i1) /dsag _(2i9)<−0.10  (7)

In the zoom lens of this embodiment, it is also preferable that theaspheric surface of the second lens group is arranged the closest to theimage plane side, and that the concave surface faces the image planeside.

In the zoom lens of this embodiment, it is also preferable that thecondition of the following Expression (8) is satisfied when dsag_(3i1)indicates an aspheric amount at the 10% effective aperture of an ^(i-th)aspheric surface of the third lens group viewed from the object side,and dsag_(3i9) indicates an aspheric amount at the 90% effectiveaperture of an ^(i-th) aspheric surface of the third lens group viewedfrom the object side.−0.24<dsag _(3i1) /dsag _(3i9)<−0.15  (8)

In the zoom lens of this embodiment, it is also preferable that thecondition of the following Expression (9) is satisfied when dsag_(4i1)indicates an aspheric amount at the 10% effective aperture of an ^(i-th)aspheric surface of the fourth lens group viewed from the object side,and dsag_(4i9) indicates an aspheric amount at the 90% effectiveaperture of an ^(i-th) aspheric surface of the fourth lens group viewedfrom the object side.−0.45<dsag _(4i1) /dsag _(4i9)<−0.13  (9)

In the zoom lens of this embodiment, it is also preferable that thecondition of the following Expression (10) is satisfied when RIHindicates an image height, Sg_(i) indicates a specific gravity of eachlens and CL_(i) indicates a lens diameter of each lens in the third lensgroup. $\begin{matrix}{{\sum\limits_{i = 1}^{n}{\left( {{Sg}_{i} \cdot {CL}_{i}^{2}} \right)/{RIH}}} < 50} & (10)\end{matrix}$

The following is a more detailed explanation of a zoom lens according tothis embodiment, illustrated by specific examples.

EXAMPLE 1

Table 1 below shows a specific numerical example of a zoom lensaccording to this example. TABLE 1 Group Surface r d n ν Sg CL 1 152.574 1.30 1.84666 23.9 2 29.062 6.00 1.48749 70.4 3 −428.263 0.15 428.204 3.80 1.77250 49.6 5 93.817 variable 2 6 93.817 0.70 1.80610 33.37 6.295 3.55 8 −20.692 0.70 1.69680 55.6 9 100.000 0.20 10 27.934 2.501.84666 23.9 11 −13.282 1.00 1.66547 55.2 12 79.253 variable ap. stop 13— 1.65 3 14 9.655 2.50 1.60602 57.5 3.09 3.75 15 −19.001 2.35 16 19.8791.30 1.48749 70.4 2.45 3.60 17 −700.000 0.70 1.84666 23.9 3.49 3.40 188.208 variable 4 19 11.189 1.70 1.69680 55.6 20 700.000 1.00 1.8051825.4 21 36.974 1.80 1.60602 57.5 22 −38.063 variable 5 23 ∞ 2.70 1.5163364.1 24 ∞ —

In Table 1, r (mm) denotes the radius of curvature of the lens surfaces,d (mm) denotes the lens thickness or the air distance between lenses, ndenotes the refractive index of the lenses at the d-line, and ν denotesthe Abbe number of the lenses at the d-line (this also applies toExamples 2 to 4 below).

Table 2 below lists the aspheric coefficients for the zoom lens of thisexample. TABLE 2 Surface 12 14 15 22 K  0.00000E+00 −3.45053E−01−2.50386E+00 −1.83155E+02 D −1.23365E−04 −2.55575E−04 −8.71189E−05−2.16340E−04 E −1.24521E−06  2.29320E−06  5.71117E−07  1.48111E−05 F 3.06330E−08 −6.14819E−07 −4.72710E−07 −3.17582E−07 G −1.68776E−09 4.25557E−09  0.00000E+00  0.00000E+00

Table 3 below lists the air distances (mm) that can be varied by zoomingin the case where the object point is located at infinity when measuredfrom a lens tip. The standard position in Table 3 below is the positionat which the zoom factor of the second lens group becomes x−1. In Table3 below, f (mm), F/No, and ω (°) respectively denote the focus distance,the F number, the incident half field angle at the wide-angle end, thestandard position and the tele end of the zoom lens in Table 1 (thisalso applies to Examples 2 to 4 below). TABLE 3 wide-angle end standardtele end f 4.658 23.539 55.300 F/NO 2.840 2.826 2.832 2ω 64.718 13.4745.726 d5 0.700 20.736 26.500 d10 26.500 7.464 1.700 d14 7.500 4.1557.440 d19 2.000 5.345 2.060

FIG. 3 shows a zoom lens configured on the basis of data shown in theabove Table 1. In FIG. 3, a group of lenses indicated as r1-r5 compose afirst lens group, a group of lenses indicated as r6-r12 compose a secondlens group, a group of lenses indicated as r14-r18 compose a third lensgroup, and a group of lenses indicated as r19-r22 compose a fourth lensgroup. Also in FIG. 3, optical components indicated as r23 and r24 areflat plates equivalent to an optical low-pass filter and a face plate ofCCD.

FIGS. 4 to 6 are aberration graphs for the wide-angle end, the standardposition and the tele end of the zoom lens in this example. In thesefigures, A is the graph for the spherical aberration, and shows thevalue at the d-line. B is the graph for the astigmatism; the solid curveindicates the sagittal image plane curvature, and the broken curveindicates the meridional image plane curvature. C is the graph for thedistortion. D is the graph for the longitudinal chromatic aberration;the solid curve indicates the value for the d-line, the short brokencurve indicates the value for the F-line, and the long broken curveindicates the value for the C-line. E is the graph for the lateralchromatic aberration; the short broken curve indicates the value for theF-line, and the long broken curve indicates the value for the C-line(these also apply to Examples 2 to 4 below).

As becomes clear from the aberration graphs in FIGS. 4 to 6, the zoomlens of this example has sufficient aberration correcting capability forachieving a high resolution.

FIGS. 7A-7C show the aberration graphs during a camera shake correctionof 0.31° at the tele end. FIG. 7A is a graph of the lateral aberrationat a relative image height of 0.75, FIG. 7B is a graph of the lateralaberration at image plane center, and FIG. 7C is a graph of the lateralaberration at a relative image height of −0.75; the solid curveindicates the value for the d-line, the short broken curve indicates thevalue for the F-line, the long broken curve indicates the value for theC-line, and the dash-dotted curve indicates the value for the g-line(these also apply to Examples 2 to 4 below).

As becomes clear from the aberration graphs shown in FIGS. 7A-7C, thezoom lens of this example has favorable aberration properties even whilecorrecting camera shake.

The following are the values for the conditional expressions for thezoom lens of this example.τ₃₇₀=0.14τ₃₈₀=0.48|f ₂ /RIH|=2.912|f ₂ /f ₁|=0.197f ₁₁₋₁₂ /f ₁=4.84f ₁₃₂ /f ₁₃=−2.385dsag ₂₁₁ /dsag ₂₁₉=−0.186dsag ₃₁₁ /dsag ₃₁₉=−0.176dsag ₃₂₁ /dsag ₃₂₉=−0.218dsag ₄₁₁ /dsag ₄₁₉=−0.181${\sum\limits_{i = 1}^{n}{\left( {{Sg}_{i} \cdot {CL}_{i}^{2}} \right)/{RIH}}} = 41.3$

EXAMPLE 2

Table 4 below shows a specific numerical example of a zoom lensaccording to this example. TABLE 4 Group Surface r d n ν Sg CL 1 154.725 1.30 1.84666 23.9 2 29.679 6.00 1.48749 70.4 3 −307.125 0.15 428.212 3.80 1.77250 49.6 5 92.607 variable 2 6 92.067 0.70 1.80610 33.37 6.314 3.55 8 −17.642 0.70 1.69680 55.6 9 −70.000 0.20 10 30.350 2.501.84666 23.9 11 −13.036 1.00 1.66547 55.2 12 40.000 variable ap. stop 13— 1.65 3 14 9.504 2.50 1.60602 57.5 3.09 3.70 15 −17.913 2.35 16 26.3911.30 1.48749 70.4 2.45 3.40 17 −700.000 0.70 1.84666 23.9 3.49 3.20 188.314 variable 4 19 10.867 1.70 1.69680 55.6 20 700.000 1.00 1.8466623.9 21 32.370 1.80 1.60602 57.5 22 −34.831 variable 5 23 ∞ 2.70 1.5163364.1 24 ∞ —

Table 5 below lists the aspheric coefficients for the zoom lens of thisexample. TABLE 5 Surface 12 14 15 22 K  0.00000E+00 −3.92587E−01−2.56247E+00 −1.34562E+02 D −1.34759E−04 −2.59655E−04 −8.58969E−05−1.82759E−04 E −1.15418E−06  2.00442E−06  9.52159E−08  1.30906E−05 F 1.95786E−08 −6.71309E−07 −5.51053E−07 −2.63083E−07 G −1.44027E−09 2.57405E−09  0.00000E+00  0.00000E+00

Table 6 below lists the air distances (mm) that can be varied by zoomingwhen the object point is located at infinity as measured from a lenstip. TABLE 6 wide-angle end standard tele end f 4.687 23.835 55.776 F/NO2.843 2.834 2.838 2ω 64.304 13.286 5.668 d5 0.700 20.745 26.500 d1026.500 7.455 1.700 d14 7.500 4.126 7.469 d19 2.000 5.374 2.301

FIGS. 8 to 10 are aberration graphs for the wide-angle end, the standardposition and the tele end of the zoom lens in this example.

As becomes clear from the aberration graphs in FIGS. 8 to 10, the zoomlens of this example has sufficient aberration correcting capability forachieving a high resolution.

FIGS. 11A-11C show the aberration graphs during a camera shakecorrection of 0.30° at the tele end.

As becomes clear from the aberration graphs shown in FIGS. 11A-11C, thezoom lens of this example has favorable aberration properties even whilecorrecting camera shake.

The following are the values for the conditional expressions for thezoom lens of this example.τ₃₇₀=0.03τ₃₈₀=0.27|f ₂ /RIH|=2.908|f ₂ /f ₁=0.197f ₁₁₋₁₂ /f ₁=4.786f ₁₃₂ /f ₁₃=−2.341dsag ₂₁₁ /dsag ₂₁₉=−0.193dsag ₃₁₁ /dsag ₃₁₉=−0.218dsag ₃₂₁ /dsag ₃₂₉=−0.178dsag ₄₁₁ /dsag ₄₁₉=−0.177${\sum\limits_{i = 1}^{n}{\left( {{Sg}_{i} \cdot {CL}_{i}^{2}} \right)/{RIH}}} = 38.0$

Second Embodiment

A zoom lens in this embodiment includes:

a first lens group that includes a lens having negative refractive powerand a lens having positive refractive power, as well as a lens havingpositive refractive power, arranged in that order from an object side toan image plane side, the first lens group having an overall positiverefractive power and being fixed with respect to an image plane;

a second lens group having an overall negative refractive power, a zoomoperation being carried out by shifting the second lens group on anoptical axis;

an aperture stop that is fixed with respect to the image plane;

a third lens group that is made of three single lenses consisting of aconvex lens, a concave lens and a convex lens, arranged in that orderfrom the object side to the image plane side, the third lens grouphaving an overall positive refractive power and being fixed with respectto the optical axis direction when zooming or focusing; and

a fourth lens group that is made of three single lenses consisting of alens having positive refractive power, a lens having negative refractivepower and a lens having positive refractive power, arranged in thatorder from the object side to the image plane side, the fourth lensgroup having an overall positive refractive power and being shifted onthe optical axis so as to maintain the image plane that fluctuates whenthe second lens group is shifted on the optical axis and when the objectmoves, at a certain position from a reference plane.

The third lens group can be shifted in a direction perpendicular to theoptical axis in order to correct image fluctuations during camera shake.

Furthermore, the second lens group, the third lens group or the fourthlens group includes at least one aspheric surface.

Also in the zoom lens of this embodiment, it is preferable that theconditions of Expressions (3)-(10) are satisfied.

It is also preferable for the zoom lens of this embodiment that theaspheric surface of the second lens group is arranged the closest to theimage plane side, and that the concave surface faces the image planeside.

The following is a more detailed explanation of a zoom lens according tothis embodiment, illustrated by specific examples.

EXAMPLE 3

Table 7 below shows a specific numerical example of a zoom lensaccording to this example. TABLE 7 Group Surface r d n ν Sg CL 1 157.825 1.30 1.84666 23.9 2 30.271 5.45 1.48749 70.4 3 −215.251 0.15 426.919 3.80 1.77250 49.6 5 77.730 variable 2 6 82.307 0.70 1.80610 33.37 6.223 3.55 8 −28.392 0.70 1.69680 55.6 9 64.541 0.24 10 22.584 2.091.84666 23.9 11 −16.043 1.00 1.66547 55.2 12 40.111 variable ap. stop 13— 1.60 3 14 8.141 1.72 1.60602 57.5 3.09 3.90 15 −72.295 2.32 16 30.1870.70 1.71736 29.5 3.08 3.60 17 6.982 0.60 18 13.467 1.58 1.51823 59.02.53 3.50 19 80.263 variable 4 20 9.087 1.70 1.83400 37.3 21 2324.5880.20 22 −308.441 0.70 1.84666 23.9 23 8.254 0.45 24 10.330 1.82 1.6060257.5 25 −122.862 variable 5 26 ∞ 3.30 1.51633 64.1 27 ∞ —

Table 8 below lists the aspheric coefficients for the zoom lens of thisexample. TABLE 8 Surface 12 14 25 K −2.40539E+01 −3.39446E−022.94679E−01 D −9.44918E−05 −1.83964E−04 −1.44338E−04  E −1.74618E−06 7.45147E−07 1.40336E−06 F −2.30285E−08 −1.53778E−07 −1.25465E−07  G−5.50990E−10  3.37757E−09 3.72879E−09

Table 9 below lists the air distances (mm) that can be varied by zoomingwhen the object point is located at infinity as measured from a lenstip. TABLE 9 wide-angle end standard tele end f 4.690 24.135 55.731 F/NO2.840 2.863 2.829 2ω 64.346 13.242 5.722 d5 0.700 20.733 26.500 d1027.500 7.467 1.700 d14 7.500 3.846 7.441 d19 2.000 5.654 2.059

FIG. 12 shows a zoom lens configured on the basis of data of the aboveTable 7. In FIG. 12, a group of lenses indicated as r1-r5 compose afirst lens group, a group of lenses indicated as r6-r12 compose a secondlens group, a group of lenses indicated as r14-r19 compose a third lensgroup, and a group of lenses indicated as r20-r25 compose a fourth lensgroup. In FIG. 12, optical components indicated as r26 and r27 are flatplates equivalent to an optical low-pass filter and a face plate of CCD.

FIGS. 13 to 15 are aberration graphs for the wide-angle end, thestandard position and the tele end of the zoom lens in this example.

As becomes clear from the aberration graphs in FIGS. 13 to 15, the zoomlens of this example has sufficient aberration correcting capability forachieving a very high resolution.

FIGS. 16A-16C show the aberration graphs during a camera shakecorrection of 0.33° at the tele end.

As becomes clear from the aberration graphs shown in FIGS. 16A-16C, thezoom lens of this example has favorable aberration properties even whilecorrecting camera shake.

The following are the values for the conditional expressions for thezoom lens of this example.|f ₂ /RIH|=2.911|f ₂ /f ₁|=0.197f ₁₁₋₁₂ /f ₁=4.725f ₁₃₂ /f ₁₃=−1.949dsag ₂₁₁ /dsag ₂₁₉=−0.159dsag ₃₁₁ /dsag ₃₁₉=−0.210dsag ₄₁₁ /dsag ₄₁₉=−0.185${\sum\limits_{i = 1}^{n}{\left( {{Sg}_{i} \cdot {CL}_{i}^{2}} \right)/{RIH}}} = 42.2$

Third Embodiment

A zoom lens in this embodiment includes:

a first lens group that includes a lens having negative refractive powerand a lens having positive refractive power, as well as a lens havingpositive refractive power, arranged in that order from an object side toan image plane side, the first lens group having an overall positiverefractive power and being fixed with respect to an image plane;

a second lens group that is made of a concave meniscus lens, a doubleconcave lens, a double convex lens and a convex lens, arranged in thatorder from an object side to an image plane side, having an overallnegative refractive power, a zoom operation being carried out byshifting the second lens group on an optical axis;

an aperture stop that is fixed with respect to the image plane;

a third lens group that is made of a double convex lens and a cementedlens consisting of a convex lens and a concave lens, arranged in thatorder from an object side to an image plane side, the third lens grouphaving an overall positive refractive power and being fixed with respectto the optical axis direction when zooming or focusing; and

a fourth lens group that is made of a single (convex) lens, beingshifted on the optical axis so as to maintain the image plane thatfluctuates when the second lens group is shifted on the optical axis andwhen the object moves, at a certain position from a reference plane.

The third lens group can be shifted in a direction perpendicular to theoptical axis in order to correct image fluctuations during camera shake.

Furthermore, the second lens group, the third lens group or the fourthlens group includes at least one aspheric surface.

Also in the zoom lens of this embodiment, it is preferable that theconditions of Expressions (3)-(10) are satisfied.

Also in the zoom lens of this embodiment, it is preferable that theaspheric surface of the second lens group is arranged the closest to theimage plane side, and that the concave surface faces the image planeside.

The following is a more detailed explanation of a zoom lens according tothis embodiment, illustrated by specific examples.

EXAMPLE 4

Table 10 below shows a specific numerical example of a zoom lensaccording to this example. TABLE 10 Group Surface r d n ν Sg CL 1 164.855 1.30 1.84666 23.9 2 27.412 6.55 1.60311 60.7 3 −149.171 0.15 422.681 3.95 1.77250 49.6 5 57.358 variable 2 6 57.358 0.70 1.83400 37.27 6.027 2.75 8 −11.431 1.00 1.66547 55.2 9 24.993 0.55 10 15.528 2.201.80518 25.4 11 −15.528 0.70 1.69680 55.6 12 97.011 variable ap. stop 13— 2.10 3 14 10.701 2.70 1.51450 63.1 2.39 3.90 15 −15.856 3.40 16 8.5302.30 1.48749 70.4 2.45 3.60 17 −700.000 0.70 1.84666 23.9 3.49 3.50 187.086 variable 4 19 9.433 2.50 1.60602 57.4 20 −51.188 variable 5 21 ∞2.70 1.51633 64.1 22 ∞ —

Table 11 below lists the aspheric coefficients for the zoom lens of thisexample. TABLE 11 Surface 8 14 15 19 20 K 2.90787E−01 −1.39931E+00−9.66288E−01 −5.30841E−01  −4.53023E+01  D 7.42659E−05 −1.76234E−04−1.07190E−04 2.18369E−05 5.43407E−05 E −9.45583E−06   5.34872E−07−1.16524E−06 4.25755E−06 4.79802E−06 F 4.14403E−07 −5.48708E−07−4.24862E−07 −1.82715E−07  −2.64861E−07  G −1.09933E−08   8.94570E−09 4.56042E−09 1.22783E−09 1.26562E−09

Table 12 below lists the air distances (mm) that can be varied byzooming object point is located at infinity as measured from a lens tip.TABLE 12 wide-angle end standard tele end f 4.674 22.932 56.934 F/NO2.816 2.711 2.818 2ω 65.030 13.890 5.534 d5 1.000 16.547 21.060 d1021.500 5.953 1.440 d14 7.200 3.314 7.298 d19 1.000 4.869 0.902

FIG. 17 shows a zoom lens configured on the basis of data of the aboveTable 10. In FIG. 17, a group of lenses indicated as r1-r5 compose afirst lens group, a group of lenses indicated as r6-r12 compose a secondlens group, a group of lenses indicated as r14-r18 compose a third lensgroup, and a group of lenses indicated as r19-r20 compose a fourth lensgroup. In FIG. 17, optical components indicated as r21 and r22 are flatplates equivalent to an optical low-pass filter and a face plate of CCD.

FIGS. 18 to 20 are aberration graphs for the wide-angle end, thestandard position and the tele end of the zoom lens in this example.

As becomes clear from the aberration graphs in FIGS. 18 to 20, the zoomlens of this example has sufficient aberration correcting capability forachieving a very high resolution.

FIGS. 21A-21C show the aberration graphs during a camera shakecorrection of 0.31° at the tele end.

As becomes clear from the aberration graphs shown in FIGS. 21A-21C, thezoom lens of this example has favorable aberration properties even whilecorrecting camera shake.

The following are the values for the conditional expressions for thezoom lens of this example.|f ₂ /RIH|=2.261|f ₂ /f ₁|=0.186f ₁₁₋₁₂ /f ₁=3.597f ₁₃₂ /f ₁₃=−1.605dsag ₂₁₁ /dsag ₂₁₉=−0.131dsag ₃₁₁ /dsag ₃₁₉=−0.196dsag ₃₂₁ /dsag ₃₂₉=−0.219dsag ₄₁₁ /dsag ₄₁₉=−0.418dsag ₄₂₁ /dsag ₄₂₉=−0.152${\sum\limits_{i = 1}^{n}{\left( {{Sg}_{i} \cdot {CL}_{i}^{2}} \right)/{RIH}}} = 42.4$

Fourth Embodiment

FIG. 22 is a layout illustrating a configuration of a video cameraaccording to a fourth embodiment of the present invention.

As shown in FIG. 22, the video camera according to this embodimentincludes a zoom lens 221, a low-pass filter 222 and an imaging element223 arranged in this order on the image plane side of the zoom lens 221.A viewfinder 225 is connected to the imaging element 223 via a signalprocessing circuit 224. Here, for the zoom lens 221, the zoom lens (seeFIG. 3) of Example 1 having a camera shake correction function is used,and thus a video camera, which is small, light-weight and able to savepower, can be realized. Moreover, to the third lens group of the zoomlens 221, a sensor 227 for detecting camera shake is connected via anactuator for shifting the third lens group in a perpendicular directionwith respect to the optical axis.

It should be noted that in this embodiment, the zoom lens of the Example1 as shown in FIG. 3 is used, but it is also possible to use any of thezoom lenses, for example, of Examples 2-4 instead.

Fifth Embodiment

FIG. 23 illustrates a configuration of a digital still camera accordingto a fifth embodiment of the present invention.

In FIG. 23, 231 denotes a zoom lens (FIG. 3) of Example 1 having acamera shake correction function. Furthermore, 232 denotes a collapsiblelens barrel 233 denotes an optical viewfinder, and 234 denotes a shutterrespectively.

It should be noted that in this embodiment, the zoom lens of Example 1as shown in FIG. 3 is used, but it is also possible to use any of thezoom lenses, for example, of Examples 2-4 instead.

1. A zoom lens comprising: a first lens group that is made of a lenshaving negative refractive power and a lens having positive refractivepower, as well as a lens having positive refractive power, arranged inthat order from an object side to an image plane side, the first lensgroup having an overall positive refractive power and being fixed withrespect to an image plane; a second lens group having an overallnegative refractive power, a zoom operation being carried out byshifting the second lens group on an optical axis; an aperture stop thatis fixed with respect to the image plane; a third lens group that ismade of a lens having positive refractive power, as well as a lenshaving a positive refractive power and a lens having negative refractivepower, arranged in that order from the object side to the image planeside, the third lens group having an overall positive refractive powerand being fixed with respect to the optical axis direction when zoomingor focusing; and a fourth lens group that is made of a lens havingpositive refractive power, a lens having negative refractive power and alens having positive refractive power, arranged in that order from theobject side to the image plane side, the fourth lens group having anoverall positive refractive power and being shifted on the optical axisso as to maintain the image plane that fluctuates when the second lensgroup is shifted on the optical axis and when the object moves, at acertain position from a reference plane; wherein the second lens groupis made of a concave meniscus lens, a concave lens, a double convex lensand a concave lens, arranged in that order from the object side to theimage plane side, and includes at least one aspheric surface; whereinthe third lens group comprises a cemented lens having a cemented surfacewhose convex surface faces the image plane side, the third lens groupcan be shifted in a direction perpendicular to the optical axis in orderto correct image fluctuations during camera shake, and includes at leastone aspheric surface; wherein the fourth lens group comprises at leastone aspheric surface; and wherein a condition of the followingExpression (5) is satisfied when f₁ indicates a focal length of thefirst lens group, and f₁₁₋₁₂ indicates a combined focal length of afirst lens and a second lens of the first lens group viewed from theobject side3.2<f ₁₁₋₁₂ /f ₁<5.0  (5).
 2. The zoom lens according to claim 1,wherein the fourth lens group is made of a convex lens, a concave lensand a convex lens, arranged in that order from the object side to theimage plane side, and all of the lenses are cemented together.
 3. Thezoom lens according to claim 1, wherein the fourth lens group is made ofthree lenses and all of the lenses are cemented together, satisfyingconditions of the following Expressions (1) and (2) when τ₃₇₀ indicatestransmittance of light having a wavelength of 370 nm and τ₃₈₀ indicatestransmittance of light having a wavelength of 380 nm at a part of a lenswhere the thickness is 10 nm, the lens is the second in the fourth lensgroup when viewed from the object side0.02<τ₃₇₀<0.2  (1)0.2<τ₃₈₀<0.55  (2). 4-6. (canceled)
 7. The zoom lens according to claim1, wherein a condition of the following Expression (7) is satisfied whendsag_(2i1) indicates an aspheric amount at the 10% effective aperture ofan ^(i-th) aspheric surface of the second lens group viewed from theobject side, and dsag_(2i9) indicates an aspheric amount at the 90%effective aperture of an ^(i-th) aspheric surface of the second lensgroup viewed from the object side−0.23<dsag _(2i1) /dsag _(2i9)<−0.10  (7).
 8. The zoom lens according toclaim 1, wherein the aspheric surface of the second lens group is asurface arranged closest to the image plane side, and the asphericsurface being the concave surface that faces the image plane side. 9.The zoom lens according to claim 1, wherein a condition of the followingExpression (8) is satisfied when dsag_(3i1) indicates an aspheric amountat the 10% effective aperture of an ^(i-th) aspheric surface of thethird lens group viewed from the object side, and dsag_(3i9) indicatesan aspheric amount at the 90% effective aperture of an ^(i-th) asphericsurface of the third lens group viewed from the object side−0.24<dsag _(3i1) /dsag _(3i9)<−0.15  (8).
 10. The zoom lens accordingto claim 1, wherein a condition of the following Expression (9) issatisfied when dsag_(4i1) indicates an aspheric amount at the 10%effective aperture of an ^(i-th) aspheric surface of the fourth lensgroup viewed from the object side, and dsag_(4i9) indicates an asphericamount at the 90% effective aperture of an ^(i-th) aspheric surface ofthe fourth lens group viewed from the object side−0.45<dsag _(4i1) /dsag _(4i9)<−0.13  (9). 11-13. (canceled)
 14. A zoomlens comprising: a first lens group that is made of a lens havingnegative refractive power and a lens having positive refractive power,as well as a lens having positive refractive power, arranged in thatorder from an object side to an image plane side, the first lens grouphaving an overall positive refractive power and being fixed with respectto an image plane; a second lens group having an overall negativerefractive power, a zoom operation being carried out by shifting thesecond lens group on an optical axis; an aperture stop that is fixedwith respect to the image plane; a third lens group that is made of alens having positive refractive power, as well as a lens having apositive refractive power and a lens having negative refractive power,arranged in that order from the object side to the image plane side, thethird lens group having an overall positive refractive power and beingfixed with respect to the optical axis direction when zooming orfocusing; and a fourth lens group that is made of a lens having positiverefractive power, a lens having negative refractive power and a lenshaving positive refractive power, arranged in that order from the objectside to the image plane side, the fourth lens group having an overallpositive refractive power and being shifted on the optical axis so as tomaintain the image plane that fluctuates when the second lens group isshifted on the optical axis and when the object moves, at a certainposition from a reference plane; wherein the second lens group is madeof a concave meniscus lens, a concave lens, a double convex lens and aconcave lens, arranged in that order from the object side to the imageplane side, and includes at least one aspheric surface; wherein thethird lens group comprises a cemented lens having a cemented surfacewhose convex surface faces the image plane side, the third lens groupcan be shifted in a direction perpendicular to the optical axis in orderto correct image fluctuations during camera shake, and includes at leastone aspheric surface; wherein the fourth lens group comprises at leastone aspheric surface; and wherein a condition of the followingExpression (6) is satisfied when f₁₃ indicates a focal length of a thirdlens of the first lens group viewed from the object side, and f₁₃₂indicates a focal length of a surface of the third lens of the firstlens group facing the image plane viewed from the object side−2.5<f ₁₃₂ /f ₁₃<−1.5  (6).
 15. The zoom lens according to claim 14,wherein the fourth lens group is made of a convex lens, a concave lensand a convex lens, arranged in that order from the object side to theimage plane side, and all of the lenses are cemented together.
 16. Thezoom lens according to claim 14, wherein the fourth lens group is madeof three lenses and all of the lenses are cemented together, satisfyingconditions of the following Expressions (1) and (2) when τ₃₇₀ indicatestransmittance of light having a wavelength of 370 nm and τ₃₈₀ indicatestransmittance of light having a wavelength of 380 nm at a part of a lenswhere the thickness is 10 nm, the lens is the second in the fourth lensgroup when viewed from the object side0.02<τ₃₇₀<0.2  (1)0.2<τ₃₈₀<0.55  (2).
 17. The zoom lens according to claim 14, wherein acondition of the following Expression (7) is satisfied when dsag_(2i1)indicates an aspheric amount at the 10% effective aperture of an ^(i-th)aspheric surface of the second lens group viewed from the object side,and dsag_(2i9) indicates an aspheric amount at the 90% effectiveaperture of an ^(i-th) aspheric surface of the second lens group viewedfrom the object side−0.23<dsag _(2i1) /dsag _(2i9)<−0.10  (7)
 18. The zoom lens according toclaim 14, wherein the aspheric surface of the second lens group is asurface arranged closest to the image plane side, and the asphericsurface being the concave surface that faces the image plane side. 19.The zoom lens according to claim 14, wherein a condition of thefollowing Expression (8) is satisfied when dsag_(3i1) indicates anaspheric amount at the 10% effective aperture of an ^(i-th) asphericsurface of the third lens group viewed from the object side, anddsag_(3i9) indicates an aspheric amount at the 90% effective aperture ofan ^(i-th) aspheric surface of the third lens group viewed from theobject side−0.24<dsag _(3i1) /dsag _(3i9)<−0.15  (8).
 20. The zoom lens accordingto claim 14, wherein a condition of the following Expression (9) issatisfied when dsag_(4i1) indicates an aspheric amount at the 10%effective aperture of an ^(i-th) aspheric surface of the fourth lensgroup viewed from the object side, and dsag_(4i9) indicates an asphericamount at the 90% effective aperture of an ^(i-th) aspheric surface ofthe fourth lens group viewed from the object side−0.45<dsag _(4i1) /dsag _(4i9)<−0.13  (9).
 21. A video camera comprisinga zoom lens, wherein the zoom lens used is according to claim
 1. 22. Adigital still camera comprising a zoom lens, wherein the zoom lens usedis according to claim
 1. 23. A video camera comprising a zoom lens,wherein the zoom lens used is according to claim
 14. 24. A digital stillcamera comprising a zoom lens, wherein the zoom lens used is accordingto claim 14.